Which of the following ions has the smallest radius

Options

A. `Ti^(2+)`
B. `Ni^(2+)`
C. `Pt^(2+)`
D. `Zr^(2+)`

Answer

B

Explanation

`Ti^(2+) and Ni^(2+)` are in 3d series, `Zn^(2+)` is in 4d series and Pt is in 5d series of transition metals. On moving left to right in a period, ionic radius decreases, so `Ni^(2+)` has the smallest radius.